fix: correct tojson|safe usage in templates and update validator

- Remove |safe from |tojson in HTML attributes (x-data) - quotes must
  become " for browsers to parse correctly
- Update LANG-002 and LANG-003 architecture rules to document correct
  |tojson usage patterns:
  - HTML attributes: |tojson (no |safe)
  - Script blocks: |tojson|safe
- Fix validator to warn when |tojson|safe is used in x-data (breaks
  HTML attribute parsing)
- Improve code quality across services, APIs, and tests

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

models/schema/letzshop.py

@@ -12,8 +12,7 @@ Covers:
 from datetime import datetime
 from typing import Any
 
-from pydantic import BaseModel, ConfigDict, Field, field_validator
-
+from pydantic import BaseModel, ConfigDict, Field
 
 # ============================================================================
 # Credentials Schemas
@@ -28,9 +27,7 @@ class LetzshopCredentialsCreate(BaseModel):
         None,
         description="Custom API endpoint (defaults to https://letzshop.lu/graphql)",
     )
-    auto_sync_enabled: bool = Field(
-        False, description="Enable automatic order sync"
-    )
+    auto_sync_enabled: bool = Field(False, description="Enable automatic order sync")
     sync_interval_minutes: int = Field(
         15, ge=5, le=1440, description="Sync interval in minutes (5-1440)"
     )